- insidePredicate: add hasClippedOverflow=1 when reference element
clips its content (contain:paint or overflow:hidden) and the
subject overflows beyond the reference bounds
- containsPredicate: same, checking the subject (container) clips
- Reads world.clipping table to determine if the container clips
- Safe when clipping data is absent (unit test fixtures)
John Dvorak
8dae898304